X-ray single crystal goniometer



Oct. 21, 1952 H. T. EVANS, JR 2,515,136

X-RAY SINGLE CRYSTAL GONIOMETER Fiid Aug 3, 1950 WS, @215. V IN V N TOR.

GEN

Patented Oct. 21, 1952 X-RAY SINGLE CRYSTAL 'GONIOMETEB.

Howard T. Evans, Jr., WhitePlains, N. Y.,.'.assignor to PhilipsLaboratories, Inc., ,Irvington- (an-Hudson, N. Y.

Application August 3, 1950, SerialNo. 177,500

v6. Claims. (01. 250--.-5.2)

.My invention. relates to an X-ray single crystal-goniometer which is adapted to resolvelall ofthe diffraction eiiects of a single crystal.

Accuracy of results. in analyzing crystal structure; data is being emphasized to an ever greater degree in accurately determining the structure of, acgiven'crystalline specimen. Accuracy of results in turn depends upon the accuracy of measurements made with. available instruments and since available instruments are incapable of sufficient refinement to achieve desired accuracy, it has become necessary to devise new instruments.

Accordingly, it is an object of my invention to provide anew goniometer construction for single crystal diffractionstudy which is capable of improved accuracy.

ltvisanother object of my invention to provide a modification of an existin single crystal goniometer which is. capable of measuring the intensity of diffracted radiation with greater precision.

These and further objects of my invention will appear as the specification progresses Heretofore, in single crystal diffraction study, it has been conventional to employ a film mounted in a holder andmovable with respect to the crystal as the crystal is rotated for recording diffraction beams from the crystal in order to obtain a series of patterns which unequivocally identified the crystal lattice; Thus, as the crystal'is rotated, the film holder, which is mounted on a movable carriage, is moved past the crystal so that a series of patterns is re= corded upon the film which corresponds to the various positions of the crystal. However, since films have been developed tofa'point where increased sensitivity cannot be expected, weak diffraction beams often are not recorded on the film and much valuable data is lost. Moreover, the blackening of thefilm is not directly proportional to the intensity of radiation due to various'factors.

In accordance with the present invention, I employ a Geiger-Muller tube for making intensity measurements of the. diffracted beam in connection with a single crystal-goniometer. Since the Geiger lviiiller tube has a very much greater sensitivity than films sensitive to 'X-radiation, it is possible to measure the intensities of much weaker beams and to measure relative intensities of diffracted beams more precisely and thereby enlarge the quantity of "data available from the 7 X-ray examinationofua-sing-le crystal.

"In the preferred embodiment of the invention,

the crystal is attached to aspindlegfon'rotation by'mea-ns of a universal adjustment :member about the spindle axis. A-collimator for pro- Vidlng a'parallel' beamof X-raidiation is; directed at the crystal, the axis of the. collimator-being perpendicular-to a tilt axis about which the crystal maybe tilted. The Geiger-Mulleritube is-supported on a rotatable-mounting bracket which is movable on a track perpendicular: tathe tilt axis and when the tilt is zero,, is perpendicular to the collimator axis. Various slits, and apertures are provided bSi'JWBBHlJhGWlIIdOWTOf the. Geiger-Muller tube and the: crystal to permit'thediffracted beam or a part thereofizto pass into thetube. Means are-also providedto rock the crystal through an angle required-to generate the whole difiractedbeam.

In making intensity measurementsof:therdiffracted beam three angles areirequiredz-totset' the apparatus for any particular -difiraction beam: the angularposition'of the-crystalg the angular position of the: Geiger-Muller tube;- and the tilt-angle. directly from film records made with a film holder in place of the Geiger-Muller tube.

The Geiger' Miiller tube is aligned by moving its carriage until the axis of the tube-intersects the collimator and spindle axes" after which the apparatus is locked in'this position. The three angular settings'are then fixed-fora particular difiraction' beam tobe measured: andirefined' by noting the response of the: Geiger-Muller tube and the 1 Geiger-Muller tube i locked: in position. The crystal is then rocked through an angle large enoughsothatl the wholerprofileiofj the diffracted beam is receivedbythe Geiger-Muller tube. This procedure is systematically repeated for all "reflections within the rangeof the'apparatus.

Theinvention will be described in greater detail in connection with the accompanying-drawing in'which the sole figure shows an X-ray single crystal goniometer' according to the inventi'on.

Referringto thedrawing, the goniometerzcomprisesabase i" which is adapted to be levelled by adjustable levelling screws 2 and supports a platform 3 provided with a tracki for guiding, a carriage 5 supporting a Geiger'-Miiller tube mounting bracket 6. A Geiger-Muller tube lis rotatably" supported: on the mounting bracket'and is arranged to rotate with the 'bracketiso-that its sensitive axis. 8 always :passes: through :the be set forth ,;herein" crystal 9 in a manner-to below;

These angles may bemeasured The crystal is mounted on a glass fiber secured to a universal orienting head In mounted on a spindle l which is rocked by a crank ['2 driven by an oscillating mechanism housed in an enclosure l3. The angle at which the crystal is rocked is measured on circular scale I 4.

The platform is rotatable or tiltable about an axis 15 and the angle of tilt relative to axis of the X-ray beam can be measured on circular scale IS.

A collimator ll provides a parallel beam of X-radiation which is directed at the crystal. The collimator is secured to the base of the instrument and remains in fixed position relative to the crystal. In order to limit the beam entering the Geiger-Muller tube, a slit system 8 is provided between the window of the tube and the crystal. The axis of the collimator must always intersect the tilt axis and the sensitive axis of the Geiger-Muller tube.

A further feature of the invention is that the Geiger-Muller tube carriage can be moved out of position by sliding it along the track and can be replaced by a film holder for making film records of the difiracted beam.

In order to make measurements of the diffracted beam from the crystal, the Geiger-Muller tube is replaced by a film holder by moving the carriage to the left along the track. A film holder is then positioned for making a photographic record of X-radiation difiracted by the crystal. From the photographic record thus obtained, the angular settings at which the crystal difiracts radiation can be determined. The Geiger-Muller tube is then aligned with the crystal by moving the carriage along the track until the sensitive axis of the tube intersects the collimator and spindle axis and is locked in this position. The three angular settings, i. e. the angle of inclination of the Geiger-Muller tube, the angle of tilt, and the angle of rotation of the crystal, are then approximately fixed from the angular measurements derived from the film for one beam reflected from the crystal. These angular adjustments are further refined by noting the response of the Geiger-Muller tube and the angular settings adjusted for maximum response. At this position, the Geiger-Muller tube is locked in position and the crystal then rocked through an angle large enough to develop the whole profile of the diffracted beam, i. e. the crystal is rocked generally throu h an angle of about one degree. which permits the Geiger-Muller tube to detect the shape of the diffracted beam. This procedure is then systematically repeated for all angular settin s at which reflections occur and which are Within the range of the apparatus.

The output of the Geiger-Muller tube may be recorded with conventional recording equipment and intensity measurements made of the difiracted beam.

While I have thus described my invention in a specific embodiment and with specific applica tions thereof, other modifications and applications thereof will be readily apparent to those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

What I claim is:

1. A single crystal X-ray goniometer compr1sing a base, a rotatable carriage support having a given axis of rotation, a carria e movable in a given direction along Said sup rotatable mounting bracket supported by said carriage, a Geiger-Muller tube supp by Said mounting bracket and rotatable about an axis perpendicular to said given axis, a rotatable spindle adapted to support a crystalline specimen, and collimating means for directing a parallel beam of X-radiation at said specimen, said Geiger- Miiller tube and said specimen being so arranged that the sensitive axis of the Geiger-Miiller tube, the axis of the beam of radiation and the axis of rotation of said carriage support intersect in said specimen.

2. A single crystal X-ray goniometer comprising a base, a carriage support provided with a track guide thereon and rotatable about a given axis, a carriage movable along said track guide, a rotatable mounting bracket supported by said carriage, a Geiger-Muller tube supported by said mounting bracket and rotatable about an axis perpendicular to said given axis, a rotatable spindle adapted to support a crystalline specimen, and collimating means for directing a parallel beam of X-radiation at said specimen, said collimating means having a given axis perpendicular to the axis of rotation of the support, said Geiger-Miiller tube and said specimen being so arranged that the sensitive axis of the Geiger- Miiller tube, the axis of the beam of radiation and the axis of rotation of said carriage support intersect in said specimen.

3. A single crystal X-ray goniometer comprising a base, a carriage support provided with a track guide thereon rotatable about a given axis, a carriage movable along said track guide, a mounting bracket movably supported by said carriage, said mounting bracket being rotatable about an axis perpendicular to said given axis, a Geiger-Muller tube supported by said mounting bracket, a rotatable spindle adapted to support a crystalline specimen, means to rock the spindle supporting the specimen through a given angle, and collimating means for directing a parallel beam of X-radiation at said specimen, said collimating means having a given axis perpendicular to the axis of rotation of the support, said Geiger-Muller tube and said specimen being so arranged that the sensitive axis of the Geiger- Miiller tube, the axis of the beam of radiation and the axis of rotation of said carriage support intersect in said specimen.

4. A single crystal X-ray goniometer comprising a base, a carriage support provided with a track guide thereon rotatable about a given axis, a carriage movable along said track guide, a mounting bracket movably supported by said carriage, said mounting bracket being rotatable about an axis perpendicular to said given axis, a G-eiger-Miiller tube supported by said mounting bracket, a rotatable spindle adapted to support a crystalline specimen, means to rock the spindle supporting the specimen through a given angle, collimating means for directing a parallel beam of X-radiation at said specimen, said collimating means having a given axis perpendicular to the axis of rotation of the support, said Geiger-Muller tube and said specimen being so arranged that the sensitive axis of the Geiger- Miiller tube, the axis of the collimating means and the axis of rotation of said carriage support intersect in said specimen, and means to measure the angle between the sensitive axis of the Geiger-Muller tube and the axis of the collimating means.

5. A single crystal X-ray goniometer comprising a base, a carriage support having .a given longitudinal axis and being provided with a track guide thereon, said carriage support being rotatable about an axis perpendicular to said given axis, a carriage movable along said track guide, a mounting bracket movably supported by said carriage, said mounting bracket being rotatable about an axis perpendicular to the axis of the carriage support, a Geiger-Muller tube supported by said mounting bracket, a rotatable spindle adapted to support a crystalline specimen, means to rock the spindle supporting the specimen through a given angle, collimating means for directing a parallel beam of X-radiation at said specimen, said collimating means having a given axis perpendicular to the axis of rotation of the support, said Geiger-Muller tube and said specimen bein so arranged that the sensitive axis of the Geiger-Muller tube, the axis of the collimating means and the axis of rotation of said carriage support intersect in said specimen, means to measure the angle between the sensitive axis of the Geiger-Muller tube and the axis of the collimating means, and means to measure the angle between said iven axis of said carriage support and said collimator axis.

6. A single crystal X-ray goniometer comprising a base, a carriage support having a given longitudinal axis and being provided with a track guide thereon, said carriage support being rotatable about an axis perpendicular to said given axis, a carriage movable along said track guide, a mounting bracket movably supported by said carriage, said mounting bracket being rotatable about an axis perpendicular to the axis of the carriage support, a Geiger-Muller tube supported by said mounting bracket, said Geiger-Muller tube having a given sensitive axis forming an angle with the axis of rotation of the carriage support, a rotatable spindle adapted to support a crystalline specimen, means to rock the spindle supporting the specimen through a given angle and collimating means for directing a parallel beam of X-radiation at said specimen, said collimating means having a given axis perpendicular to the axis of rotation of the support, said Geiger-Muller tube and said specimen being so arranged that the sensitive axis of the Geiger- Miiller tube, the axis of the collimating means and the axis of rotation of said carriage support intersect in said specimen, means to measure the angle between the said sensitive axis of the Geiger-Muller tube and the collimator axis, means to measure the angle between said given axis of the carriage support and said collimator axis, and means to measure the angular rotation of said specimen when rocked.

HOWARD T. EVANS, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,589,833 Behnken et a1 June 22, 1926 2,377,862 Bond June 12, 1945 2,380,235 Harker July 10, 1945 C'IHER REFERENCES GE X-Ray Corp Publication, 7A-560, June 15, 1939, pgs. 8 and 16. 

